I believe I lost most of my flock to Mercks also. Mine started out walking funny, off center, and would go down from there. They would not be able to walk straight, and were happy, but finally got to where they could not stand, they would fall over sideways. Before I figured it out, I tried to nurse one back to health, she would eat and drink when held up, and was happy, but never did recover. It's heartbreaking. I did not have any with the symptoms I saw with your bird, she seems balanced other than feet curled up. I'd go with nutritional needs. I would consider de-worming as worms could be robbing her of these. You could get her poo tested also to be sure. In the south worms can get bad fast in young birds. Not sure where your at. I find the need to keep my birds de-wormed several times a year, and every few months while they are young. I also give verm-x monthly, it's organic. Best wishes with your little gal there. Hope she recovers. Keep her isolated and watch the others closely. FYI FDA has ability to test for anything just about a chicken can have, there is no return from there though, so it would be a last resort if others start getting ill also. Anymore for the most part, I only buy birds from Murray McMurray hatchery direct and will have all of them vaccinated for Mercks and Cocciodisis. I do not want to ever again have to cull most of my flock.